The first, second, and fourth are all heavily biased/opinionated, the third is simply stating a basic mechanic of English to allow them to alter their own righting accordingly. I would recommend the third.
A good example of constructive feedback is option C. When using dialogue, you don't always need to write "he said" and "she said." The context can often indicate who is talking.
Explanation:
Giving constructive feedback is an important part of the writing process because this process allows an individual to help the writer identify solutions to his or her weaknesses. This type of feedback should be based on information or observations rather than in biased opinions or criticism. The option that best fits this requirement is C.
